When I play a movie with DTS-HD MA 5.1 audio, HDMI pass-through sends PCM to my sound system connected to my TV with ARC, and the red ‘dts’ light on my audio system is not on. If I switch the audio pass-through setting in the Plex settings to “Optical” and set the codecs to AC3 and DTS, the audio passes to the system correctly, illuminating the ‘dts’ light and making an audible difference. Keep in mind that though the pass-through setting is set to optical, there is no optical cable in this set up and the sound is sent to the receive over HDMI ARC. This is when my TV was on Android 9, which I updated to today.
Yesterday, when the TV was on Android 8, HDMI pass-through would send dts sound to the receiver, but the video would stutter and sound would cut out at the beginning. The optical setting worked fine in this case as well.
This happens for multiple movies with DTS audio. AC3 audio works fine on both optical and HDMI settings, setting the receiver to the appropriate mode.
TV is a Sony Bravia XBR-65X900E running Android 9. Receiver is an Onkyo HT-R390, using a high speed HDMI cable for ARC.
What is going on here? Right now I have pass-through set to optical just so I can get DTS sound, should I be concerned that the quality is not as good as it can be if the HDMI setting worked properly?
Both Audio and Video are direct play with either HDMI or Optical settings. When turning pass-through off the sound is transcoded. This issue did not just appear with the latest version of the app. I cannot remember if it ever worked with the HDMI setting as most of the movies I have watched lately are not DTS.
There is a bug that the optical settings are being applied to hdmi as well, that’s why it works. If you turn those setting off for optical, they also get turned off for hdmi which is likely what was happening before.
When using hdmi pass-through, the Plex app will identify what is connected to your TV to see what is supported. Your Onkyo supports DTS-HD MA so it tells this to your TV. The app then checks what the TV itself supports, but it doesn’t support DTS-HD MA. So to keep the quality, Plex will decode the DTS-HDMA into raw PCM and send that to the receiver to give it the best quality.
You can’t send DTS-HD MA over optical, so by enabling optical, PMS will convert to basic 5.1 DTS and send that.
Using the PCM audio would give you the better sound quality.
When using the optical setting, the basic dts sounded more “boomy,” while using the HDMI setting which uses PCM did not.
Would the boomyness of the dts track just be a product of the conversion? I noticed my receiver seems to have a different audio mode for DTS so maybe it could be that.
My receiver says it receives 48KHz PCM with HDMI passthrough, does this sound right?
And how come decoding to PCM doesn’t hurt quality? My receiver has several modes you can switch through when using PCM, one of them is PLII Cinema, and another is Neo 6, which turns the receivers DTS light on when using PCM, would this be a better way to listen to this DTS-HD MA sound over PCM?
Is there a way for Plex to by-pass the TV and send DTS-MA HD straight to the receiver, since the receiver supports it?
Upon some reading, specifically on this reddit thread it appears the limitation is with the TV only supporting ARC, with eARC capable of passing-through codecs such as DTS-HD MA and TrueHD. This explains why other movies I have with TrueHD need to transcode.
The only solution for this would be to use an external player like an Nvidia shield and connect it directly to the receiver, then to the TV. The problem is this specific receiver doesn’t do 4k or HDR. Or just get a new TV.
DTS-HD MA decoded to PCM through Plex will still play at 5.1 channels correct?
Once I move out and start to build my own set-up I will keep these capabilities in mind.
Upon reading the receiver manual it seems that running it in direct mode is best. The modes I listed earlier are for processing stereo signals and turning them into surround.
